The filing of criminal charges in federal court begins with an investigation of suspected criminal activity, usually conducted by the FBI. However, other federal agencies are sometimes involved depending on the type of alleged crime, such as the Drug Enforcement Agency (drug crimes) or the Securities and Exchange Commission (securities crimes). The criminal investigation develops the facts that support the issuance of search warrants. The U.S. Attorney's Office and federal grand jury become involved at this point, which often results in the filing of criminal charges either by a complaint or indictment.
Report allegations of criminal behavior to law enforcement. In federal cases, this usually means contacting the FBI, but often times local police agencies take the first reports and then turn over the case to the FBI when it appears that the criminal activity involves a violation of federal law.
Investigate the information contained in the initial reports through the appropriate law enforcement agency. For federal investigations, the FBI is usually the lead investigative agency with other agencies becoming involved as needed for their expertise, such the Bureau of Alcohol Tobacco and Firearms for bombing cases.
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Contact the U.S. Attorney's Office to apply for search warrants. An agent from the investigating agency and an assistant U.S. attorney will prepare and take an application to a magistrate judge or district court judge. The search warrant will be issued so long as the evidence provided, usually in the form of the agent's affidavit (written testimony), provides the judge with evidence of probable cause that a crime is or has been committed.
Take the evidence obtained through the investigation and execution of the search warrants to a federal grand jury in order to obtain an indictment. This is done by the assistant U.S. attorney presenting a list of the crimes the defendant allegedly committed and describing the facts to support those allegations. Grand juries are typically composed of 16 to 23 citizens, and upon agreement by a simple majority that probable cause of a crime exists, the indictment will be issued.
File the indictment with the district court and apply for an arrest warrant. Indictments usually remain sealed from public view until after the defendant is arrested.